Korean researchers from KERI and Ulsan National Institute of Science and Technology (UNIST) have developed a breakthrough technology that enables the printing of micro-patterns on contact lenses, allowing for augmented reality (AR) navigation. Unlike previous methods that were limited to films coated with electric plating, the new technology utilizes the Meniscus effect, the phenomenon where a curved surface is formed due to capillary action when water droplets are gently pressed or pulled with a certain pressure, to crystallize Prussian blue onto the lenses, producing continuous and uniform colors. The printing process can be performed on flat and curved surfaces, making it applicable to smart contact lenses. The micro-pattern technology is very fine (7.2 micrometers).
Dr. Seol Seung-Kwon’s of KERI said, “Our achievement is a development of 3D printing technology that can print functional micro-patterns on non-planner substrate that can commercialize advanced smart contact lenses to implement AR.” He added, “It will greatly contribute to the miniaturization and versatility of AR devices.”
The ink used in the printing process is acidic-ferric-ferricyanide ink, which is filled into a micronozzle and comes into contact with the substrate. Heterogeneous crystallization of FeFe(CN)6 occurs on the substrate within the meniscus via spontaneous reactions of the precursor ions (Fe3+ and Fe(CN)3−) at room temperature. The solvent evaporates from the meniscus, inducing the edge-enhanced crystallization of FeFe(CN)6, which controls the factors that influence the crystallization of FeFe(CN)6 in the printing step to obtain uniformly printed Prussian blue patterns on a substrate.
Reference
Kim, J. H., Park, S., Ahn, J., Pyo, J., Kim, H., Kim, N., Jung, I. D., Seol, S. K., Meniscus-Guided Micro-Printing of Prussian Blue for Smart Electrochromic Display. Adv. Sci. 2023, 10, 2205588. https://doi.org/10.1002/advs.202205588
